The disc type turbine is a bladeless turbine machine that operates from a pressurized fluid, e.g. liquid, gas or steam, directed by one or more nozzles in a generally tangential direction into the perimeter region of a rotor assembly of multiple closely-spaced discs, which become driven to rotate by the principle of boundary layer drag on the surfaces of the closely-spaced discs.
Initial development and usage of disc type turbines has been historically limited by relatively low efficiency, along with unavailability of disc material capable of reliably withstanding high temperatures, stresses and harsh environmental factors, e.g. when driven by super-heated steam.
Subsequent developments have resulted in the realization of somewhat higher efficiency and analysis has indicated that, in theory, disc type turbines have potential for very high operating efficiency beyond what has been realized in practice to date. Along with the development of more satisfactory disc materials, there has been a resurgence of interest in disc type turbines as candidates for present day steam-driven applications.